# A truck engine transmits 28 kW (27.5 hp) to the driving wheels when the truck is traveling at a constant velocity of magnitude 60 km/h (37.3 m/h) on a level road. (a) What is the resisting force acting on the truck? (b) Assume that 65% of the resisting force is due to rolling friction and that the remainder is due to air resistance. If the force of rolling friction is independent of speed and the force of air resistance is proportional to the square of speed, what power will drive the truck at 30 km/h? at 120 km/h? give your answers in kilowatts and in horsepower.

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A truck engine transmits 28 kW (27.5 hp) to the driving wheels when the truck is traveling at a constant velocity of magnitude 60 km/h (37.3 m/h) on a level road. (a) What is the resisting force acting on the truck? (b) Assume that 65% of the resisting force is due to rolling friction and that the remainder is due to air resistance. If the force of rolling friction is independent of speed and the force of air resistance is proportional to the square of speed, what power will drive the truck at 30 km/h? at 120 km/h? give your answers in kilowatts and in horsepower.

2021-02-24
velocity
М=6000/3600=1.6666m
force
$$\displaystyle{F}=\frac{{P}}{{V}}=\frac{{28000}}{{1.6666}}={1.68}\cdot{10}^{{{3}}}{N}$$
b) The speed is lowered by a factor ofone-half, and the resisting force is lowered by a factor of(0.65+0.35/4) and sothe power at the lower speed is
p = 28 *(0.5)(0.65+0.35/4) =10.3kw
Similarly, at the higher speed,
p = 28 *(2 )(0.65+0.35/4) = 114.8 kw

### Relevant Questions

The dominant form of drag experienced by vehicles (bikes, cars,planes, etc.) at operating speeds is called form drag. Itincreases quadratically with velocity (essentially because theamount of air you run into increase with v and so does the amount of force you must exert on each small volume of air). Thus
$$\displaystyle{F}_{{{d}{r}{u}{g}}}={C}_{{d}}{A}{v}^{{2}}$$
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Consider a vehicle moving with constant velocity $$\displaystyle\vec{{{v}}}$$. Find the power dissipated by form drag.
Express your answer in terms of $$\displaystyle{C}_{{d}},{A},$$ and speed v.
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Assume the following:
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The magnitude of the force of air drag at these speeds is proportional to the square of the speed.
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Express the percent increase in top speed numerically to two significant figures.
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Previous studies show that $$\sigma_1 = 19$$.
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$$H_0:\mu_1<\mu_2.\mu_1=\mu_2$$
$$H_0:\mu_1=\mu_2.\mu_1<\mu_2$$
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The standard normal. We assume that both population distributions are approximately normal with unknown standard deviations.
The standard normal. We assume that both population distributions are approximately normal with known standard deviations.
The Student's t. We assume that both population distributions are approximately normal with unknown standard deviations.
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At the $$\alpha = 0.01$$ level, we reject the null hypothesis and conclude the data are statistically significant.
At the $$\alpha = 0.01$$ level, we fail to reject the null hypothesis and conclude the data are statistically significant.
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Fail to reject the null hypothesis, there is insufficient evidence that there is a difference in mean pollution index for Englewood and Denver.
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lower limit
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Because the interval contains both positive and negative numbers, this indicates that at the 99% confidence level, the mean population pollution index for Englewood is greater than that of Denver.
Because the interval contains only negative numbers, this indicates that at the 99% confidence level, the mean population pollution index for Englewood is less than that of Denver.
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